Fertilization facts for kids

Human sperm arrives at the egg cell.

Liverworts are a kind of small plant with a complex life cycle that includes fertilization. The sperm and the egg come together to make a zygote. The zygote grows into an embryo.

Fertilization is a key step in how living things reproduce. It happens when a male's tiny sperm cell joins with a female's ovum (or "egg") cell. This joining creates a new cell called a zygote. The zygote then starts to grow and develop into an embryo.

Fertilization happens in many different living things, including animals (like humans and birds), plants, fungi, and tiny protists. It's a process that helps create new life. When the sperm and egg join, they combine their genetic information, which helps the new organism grow with traits from both parents.

Fertilization in Animals

In animals, there are two main ways fertilization can happen: internal and external.

Internal Fertilization

Internal fertilization means the sperm and egg join inside the female's body. This happens in many animals, including mammals (like humans, dogs, and cats), birds, and reptiles (like snakes and lizards).

During internal fertilization, the male and female animals usually come together for mating. Sperm cells travel from the male into the female's body. One sperm then joins with an egg inside the female. After fertilization, some animals, like humans and most mammals, give birth to live babies. Other animals, like birds, most reptiles, and some mammals such as the Platypus, lay eggs that hatch later. These eggs are usually fertilized before they are laid.

External Fertilization

External fertilization means the sperm and egg join outside the female's body, usually in water. This is common for amphibians (like frogs) and most fish.

For external fertilization, the male and female release their sperm and eggs into the water at the same time. The sperm then swim to find and fertilize the eggs in the water.

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  Coral animals release their eggs and sperm into the water. They meet in the currents to fertilize and grow into new coral.

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  Most fish fertilize their eggs externally. The eggs and sperm are put into the water at the same time.

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  Bird eggs are usually fertilized before they are laid.

Related topics

• Alternation of generations
• Mating

Images for kids

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  In Bryophyte land plants like moss, fertilization happens inside a special part called the archegonium.

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  Red-veined darters (Sympetrum fonscolombii) flying together. The eggs are fertilized as they are laid, one at a time.

See also

In Spanish: Fecundación para niños